Portable gas fractionalization system

ABSTRACT

A portable gas fractionalization apparatus that provides oxygen rich air to patients is provided. The apparatus is compact, lightweight, and low-noise. The components are assembled in a housing that is divided into two compartments. One compartment is maintained at a lower temperature than the other compartment. The lower temperature compartment is configured for mounting components that can be damaged by heat. The higher temperature compartment is configured for mounting heat generating components. An air stream is directed to flow from an ambient air inlet to an air outlet constantly so that there is always a fresh source of cooling air. The apparatus utilizes a PSA unit to produce an oxygen enriched product. The PSA unit incorporates a novel single ended column design in which all flow paths and valves can be co-located on a single integrated manifold. The apparatus also can be used in conjunction with a satellite conserver and a mobility cart.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a portable gas fractionalizationsystem, more particularly, to a compact oxygen concentrator that issuitable for both in-home and ambulatory use so as to provide usersgreater ease of mobility.

2. Description of the Related Art

Patients who suffer from respiratory ailments such as ChronicObstructive Pulmonary Diseases (COPD) often require prescribed doses ofsupplemental oxygen to increase the oxygen level in their blood.Supplemental oxygen is commonly supplied to the patients in metalcylinders containing compressed oxygen gas or liquid oxygen. Eachcylinder contains only a finite amount of oxygen that typically lastsonly a few hours. Thus, patients usually cannot leave home for anylength of time unless they carry with them additional cylinders, whichcan be heavy and cumbersome. Patients who wish to travel often have tomake arrangements with medical equipment providers to arrange for anexchange of cylinders at their destination or along the route, theinconvenience of which discourages many from taking extended trips awayfrom home.

Supplemental oxygen can also be supplied by oxygen concentrators thatproduce oxygen concentrated air on a constant basis by filtering ambientair through a molecular sieve bed. While oxygen concentrators areeffective at continual production of oxygen, they are typically largeelectrically powered, stationary units that generate high levels ofnoise, in the range of 50–55 dB, which presents a constant source ofnoise pollution. Moreover, the units are too heavy to be easilytransported for ambulatory use as they typically weigh between 35 to 55lbs. Patients who use oxygen concentrators are thus tethered to thestationary machines and inhibited in their ability to lead an activelife. While portable oxygen concentrators have been developed to providepatients with greater mobility, the currently commercially availableportable concentrators do not necessarily provide patients with the easeof mobility that they desire. The portable concentrators tend togenerate as much noise as the stationary units and thus cannot be usedat places such as the theater or library where such noise is prohibited.Moreover, the present portable concentrators have very short batterylife, typically less than one hour, and thus cannot be used continuouslyfor any length of time without an external power source.

From the foregoing, it will be appreciated that there is a need for anapparatus and method that effectively provide supplemental oxygen topatients for both in-home and ambulatory use. To this end, there is aparticular need for a portable oxygen concentrator that is lightweight,quiet, and can supply oxygen continuously for an extended period withoutrequiring an external power source.

SUMMARY OF THE INVENTION

In one aspect, the preferred embodiments of the present inventionprovide a portable gas fractionalization apparatus comprising a PSA unithaving plural adsorbent beds which produce oxygen having a purity of atleast 87%; a compressor connected to supply compressed air to the PSAunit; and a blower which produces an air stream across the compressor.The PSA unit comprises valves operating in accordance with a PSA cyclethat includes a pressure equalization step so as to provide greater thanabout 31% recovery of oxygen from air. Preferably, the valves of the PSAunit are disposed upstream of the air stream across the compressor suchthat thermal load on the PSA valves is reduced. Preferably, thecompressor is a non-reciprocating compressor so as to reduce compressornoise, wherein the compressor is configured to draw ambient air at aflow rate of no more than about 15 slpm.

In one embodiment, the PSA unit comprises two adsorbent beds thatoperate in accordance with a six-step PSA cycle. Preferably, the PSAunit provides between about 31%–38% recovery of oxygen from air andproduces an oxygen having a purity of between about 87%–93%. In anotherembodiment, the compressor comprises a scroll compressor configured tosupply the compressed air to the PSA unit at a flow rate of betweenabout 4 to 9 slpm and at a pressure of about 35 psia while generating anoise level of less than about 35 dB external to the compressor. Incertain embodiments, the apparatus further comprises a heat exchangerwhich cools the compressed air to about the temperature of the ambientair prior to supplying the compressed air to the PSA unit. Moreover, theapparatus may also include a product gas delivery system which deliversoxygen to the patient at a flow rate of between about 0.15–0.75 slpm; amicroprocessor control for recording data on apparatus performance orusage; and an infrared I/O port for transmitting the data to a remotelocation.

In a second aspect, the preferred embodiments of the present inventionprovide a portable gas fractionalization apparatus comprising a housinghaving an air inlet and an air outlet wherein the housing is configuredsuch that noise produced exterior to the fractionalization apparatus isno more than about 45 dB. The housing preferably contains componentsincluding a compressor, plural adsorbent beds, a battery having a ratedlife of at least 2 hours. The compressor is powered by the battery so asto draw air into the compressor preferably at a rate of about 15 slpm orless. Moreover, the housing and the components preferably have acombined weight of less than about 10 pounds.

In one embodiment, the apparatus further comprises a blower which isconfigured to draw ambient air through the air inlet to provide coolingfor the components. Preferably, the housing comprises a circuitous airflow passageway for the ambient air to flow through, wherein thecircuitous passageway extends between the air inlet and the air outletand is configured to reduce noise due to air flow. In anotherembodiment, the compressor is preferably a scroll compressor configuredto deliver a feed gas at a flow rate of between about 4 to 9 slpm and ata pressure of about 35 psia while generating a noise level of less thanabout 35 dB external to the compressor. In certain embodiments, theapparatus further comprises a plurality of sound baffles. Moreover, thehousing may also comprise a vibration damper to reduce transfer ofvibrational energy from the compressor to the housing.

In a third aspect, the preferred embodiments of the present inventionprovide a method of producing an oxygen rich gas. The method comprisesproviding ambient air to a non-reciprocating compressor, wherein theambient air is drawn into the compressor at a flow rate of less thanabout 15 slpm. The compressor pressurizes the ambient air and deliversthe pressurized air to a PSA unit preferably at a flow rate of betweenabout 4 to 9 slpm. The method further comprises processing thepressurized air in the PSA unit in accordance with a PSA cycle so as toproduce an oxygen rich gas having a purity of between about 87%–93%. Inone embodiment, the PSA cycle includes a pressure equalization step. Inanother embodiment, the PSA cycle is a six-step/two bed cycle.Preferably, the PSA unit operating in accordance with the PSA cycleprovides greater than about 31% recovery of oxygen from the ambient air.In certain embodiments, the method further comprises generating an airstream across the compressor to provide cooling for the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a portable gas fractionalization system ofone preferred embodiment of the present invention;

FIG. 2 is a perspective view of a portable gas fractionalizationapparatus of another preferred embodiment, which is shown in the form ofan oxygen concentrator;

FIG. 3 is a perspective view of the apparatus of FIG. 2 as seen with theshell removed;

FIG. 4 is a perspective view of the chassis of the apparatus of FIG. 2;

FIG. 5 is a perspective view of the components inside the firstcompartment of the apparatus of FIG. 2, showing a PSA unit;

FIG. 6 is a schematic illustration of an adsorbent bed column of the PSAunit of FIG. 5;

FIGS. 7A and 7B are schematic diagrams of gas flow to and from theadsorbent bed column of FIG. 6;

FIG. 8 is a detailed view of the integrated manifold of the PSA unit ofFIG. 5;

FIG. 9 is a schematic illustration of a water trap system incorporatedin the integrated manifold of FIG. 8;

FIG. 10 is a schematic illustration of a piloted valve systemincorporated in the integrated manifold of FIG. 8;

FIG. 11 is a perspective view of the components inside the secondcompartment of the apparatus of FIG. 2, showing a compressor system;

FIG. 12 is a perspective view of a vibration damping member incorporatedin the compressor system of FIG. 11;

FIG. 13 is a perspective view of the components assembled in the housingof the apparatus of FIG. 2;

FIG. 14 is a schematic diagram of a directed ambient air flow throughthe housing of the apparatus of FIG. 2, illustrating a thermalmanagement system of one preferred embodiment;

FIG. 15 is a schematic diagram of a gas flow through the components ofthe apparatus of FIG. 2;

FIG. 16A is perspective view of the apparatus of FIG. 2, showing anin-line filter integrated in the shell of the apparatus;

FIG. 16B is a detailed view of the in-line filter of FIG. 16B;

FIG. 16C is a perspective view of the apparatus of FIG. 2, showing aremovable hatch;

FIG. 17 is a schematic illustration of a satellite conserver used inconjunction with the apparatus of FIG. 2;

FIGS. 18A and 18B are schematic illustrations of a mobility cart used inconjunction with the apparatus of FIG. 2 for transporting the apparatus.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 schematically illustrates a portable gas fractionalization system100 of one preferred embodiment of the present invention. As shown inFIG. 1, the system 100 generally comprises an intake 102 through whichambient air is drawn into the system, a filter 104 for removingparticulate from the intake air, a compressor assembly 106 forpressurizing the intake air to provide a feed gas, a pressure swingadsorption (PSA) unit 108 which receives and processes the feed gas toproduce a product gas having a higher oxygen content than the ambientair, and a gas delivery system 110 for delivering the product gas to apatient.

Ambient air is drawn through the intake 102 at a relatively low flowrate, preferably no greater than about 15 standard liters per minute(slpm), so as to reduce noise due to airflow through the system. Thesystem 100 further includes a fan 112 that produces an air stream acrossthe compressor assembly 106 also preferably at a relatively low flowrate so as to provide cooling for the compressor assembly 106 withoutgenerating excessive noise.

As also shown in FIG. 1, the compressor assembly 106 includes acompressor 114 and heat exchanger 116. The compressor 114 is preferablya non-reciprocating compressor, more preferably a scroll compressordescribed in U.S. Pat. Nos. 5,759,020 and 5,632,612, which are herebyincorporated by reference in their entirety. It is generally understoodthat a scroll compressor operates by moving a plate such that it orbitsin a single plane relative to a fixed plate. Thus, the use of a scrollcompressor advantageously eliminates reciprocating motion that tends togenerate the excessive noise and vibration associated with manyconventional piston compressors. In one embodiment, the scrollcompressor 114 delivers an air flow of between about 4 to 9 slpm at apressure of about 35 psia, while generating a noise level of less thanabout 35 dB external to the compressor. The scroll compressor 114 doesnot require lubricating oil and thus operates in a substantiallyoil-free environment, which advantageously reduces the likelihood ofintroducing oil contaminants into the compressed air. As FIG. 1 furthershows, the compressor 114 works in conjunction with the heat exchanger116 to provide cooled feed gas to the PSA unit 108. In one embodiment,the heat exchanger 116 has a large thermally conductive surface that isin direct contact with the air stream produced by the fan 112 such thatpressurized air traveling through the heat exchanger 116 can be cooledto a temperature close to ambient prior to being supplied to the PSAunit 108.

The PSA unit 108 is configured to operate in accordance with a pressureswing adsorption (PSA) cycle to produce an oxygen enriched product gasfrom the feed gas. The general operating principles of PSA cycles areknown and commonly used to selectively remove one or more components ofa gas in various gas fractionalization devices such as oxygenconcentrators. A typical PSA cycle entails cycling a valve systemconnected to at least two adsorbent beds such that a pressurized feedgas is sequentially directed into each adsorbent bed for selectiveadsorption of a component of the gas while waste gas from previouscycles is simultaneously purged from the adsorbent bed(s) that are notperforming adsorption. Product gas with a higher concentration of theun-adsorbed component(s) is collected for use. Additional backgroundinformation on PSA technology is described in U.S. Pat. No. 5,226,933,which is hereby incorporated by reference.

As shown in FIG. 1, the PSA unit 108 of a preferred embodiment includestwo adsorbent beds 118 a, 118 b, each containing an adsorbent materialthat is selective toward nitrogen, and a plurality of valves 120 a–jconnected thereto for directing gas in and out of the beds 118 a, 118 b.As will be described in greater detail below, the valves 120 a–jpreferably operate in accordance with a novel PSA cycle which comprisesa six step/two bed process that includes a pressure equalization step inwhich a portion of the effluent product gas from one bed is diverted topressurize another bed in order to improve product recovery and reducepower consumption. One preferred embodiment of the PSA cycle comprisesthe following steps:

Step 1: Pressurize-Adsorbent Bed 118 a/Production-Adsorbent Bed 118 b

-   -   pressurizing adsorbent bed 118 a by directing feed gas into        adsorbent bed 118 a in the co-current direction at a feed        pressure of about 35 psia while simultaneously diverting oxygen        enriched product gas of higher pressure from adsorbent bed 118 b        into adsorbent bed 118 a in the counter-current direction until        pressures of the two beds 118 a, 118 b are substantially        equalized;    -   releasing product gas from adsorbent bed 118 b to a storage        vessel 124 while stopping the flow of feed gas from entering        adsorbent bed 118 b;

Step 2: Feed-Adsorbent Bed 118 a/Blowdown-Adsorbent Bed 118 b

-   -   feeding adsorbent bed 118 a with feed gas at a rate of about        4–8.5 slpm at a feed pressure of about 35 psia;    -   counter-currently releasing nitrogen enriched waste gas from        adsorbent bed 118 b to an exhaust muffler 122;

Step 3: Feed and Production-Adsorbent Bed 118 a/Purge-Adsorbent Bed 118b

-   -   releasing product gas from adsorbent bed 118 a to the storage        vessel 124 while continuing to feed adsorbent bed 118 a with        feed gas at a rate of about 4–8.5 slpm. at a feed pressure of        about 35 psia;    -   purging adsorbent bed 118 b by releasing product gas from the        storage vessel 124 to adsorbent bed 118 b while continuing to        counter-currently release waste gas from adsorbent bed 118 b to        the exhaust muffler 122;

Step 4: Production-Adsorbent Bed 118 a/Pressurize-Adsorbent Bed 118 b

-   -   continuing to release product gas from adsorbent bed 118 a to        the storage vessel 124 while stopping the flow of feed gas from        entering adsorbent bed 118 a;    -   pressurizing adsorbent bed 118 b by directing feed gas into        adsorbent bed 118 b in the co-current direction at a feed        pressure of about 35 psia while simultaneously diverting product        gas of higher pressure from adsorbent bed 118 a into adsorbent        bed 118 b in the counter-current direction until pressures of        the two beds 118 a, 118 b are substantially equalized;

Step 5: Blowdown-Adsorbent Bed 118 a/Feed-Adsorbent Bed 118 b

-   -   counter-currently releasing waste gas from adsorbent bed 118 a        to the exhaust muffler 122;    -   feeding adsorbent bed 118 b with feed gas at a rate of about        4–8.5 slpm at a feed pressure of about 35 psia;

Step 6: Purge-Adsorbent Bed 118 a/Feed and Production-Adsorbent Bed 118b

-   -   releasing product gas from adsorbent bed 118 b to the storage        vessel 124 while continuing to feed adsorbent bed 118 b with        feed gas at a rate of about 4–8.5 slpm at a feed pressure of        about 35 psia;    -   purging adsorbent bed 118 a by releasing product gas from the        storage vessel 124 to adsorbent bed 118 a while continuing to        counter-currently release waste gas from adsorbent bed 118 a to        the exhaust muffler 122;

The PSA cycle described above advantageously includes one or morepressure equalization steps (steps 1 and 4) in which already pressurizedproduct gas is released from one adsorbent bed to provide initialpressurization for another adsorbent bed until the two beds have reachedsubstantially the same pressure. The pressure equalization step leads toincreased product recovery and lower power consumption because itcaptures the expansion energy in the product gas and uses it topressurize other adsorbent beds, which in turn reduces the amount ofpower and feed gas required to pressurize each bed. In one embodiment,the two-bed PSA unit shown in FIG. 1 operating in accordance with theabove-described six-step/two-bed PSA cycle is capable of producingoxygen having a purity of at least about 87%, preferably between about87%–93%, with greater than about 31% recovery of oxygen from feed gas,more preferably greater than about 38% recovery. In operation, thevalves 120 a–j of the PSA unit 108 are controlled in a known manner toopen and close for predetermined time periods in accordance with theabove described PSA steps. Additionally, the valves 120 a–j arepreferably positioned upstream of the air stream produced by the fan 112across the compressor assembly 106 so as to not expose the valves 120a–j to portions of the air stream that are heated by the compressorassembly 106. In other embodiments, the system may utilize a vacuumswing adsorption (VSA) unit or a vacuum-pressure swing adsorption (VPSA)unit to produce the oxygen rich product gas.

As FIG. 1 further shows, the product gas produced by the PSA unit 108 isdelivered to a patient via the product gas delivery system 110. Theproduct gas delivery system 110 generally includes an oxygen sensor 126for monitoring the oxygen content of the product gas exiting the storagevessel 124, a delivery valve 128 for metering the product gas to thepatient, an in-line filter 130 for removing fine particulate in theproduct gas immediately prior to delivery to the patient, a conserverdevice 132 that controls the amount and frequency of product gasdelivered based on the patient's breathing pattern. In certainembodiments, the product gas delivery system may also incorporate a unitthat measures pressure within the storage vessel which in turn dictatesthe rate at which product gas is driven through the delivery valve.Preferably, product gas is delivered to the patient at a flow rate ofabout 0.15–0.75 slpm at about 90% oxygen content. In one embodiment, thesystem 100 also includes a microprocessor control 134 for collecting andrecording data on system performance or patient usage pattern and aninfrared port 136 for transmitting the data to a remote location.

FIG. 2 illustrates a gas fractionalization apparatus 200 of thepreferred embodiment, which is shown in the form of a portable oxygenconcentrator. As illustrated in FIG. 2, the apparatus 200 generallycomprises a chassis 202 (see also FIG. 3) and a shell 204 that togetherform a housing 206 in which various components are mounted. The chassis202 is removably attached to a base 208 of the housing 206. The base 208has a substantially planar exterior bottom surface adapted to restagainst a support surface such as a table or floor. The shell 204 of thehousing 206 further includes an upper wall 210 and side walls 212 a–d,each having at least one convex and/or concave section that provides acurvature to the wall so as to reduce coupling of sound or vibrationenergy generated by the components in the housing. Such curvature isalso effective to reduce constructive interference of the coupled energywithin the walls. Accordingly, the lack of planar sections in the walls210, 212 a–d of the housing 206 that are conducive to vibration reducesnoise induced by vibration. Moreover, the non-planar walls 210, 212 a–dalso serve to discourage users from setting the housing on its side orplacing it in any orientation other than the upright as the componentsinside the housing are designed to operate optimally in the uprightorientation, which will be described in greater detail below.

As shown in FIG. 3, the components in the housing 206 are structurallysupported by the chassis 202 and the chassis 202 is removably attachedto the shell 204. As such, the components can be assembled outside theconfines of the shell 204. Also, the shell can be conveniently removedto provide access for testing, repair, or maintenance of the components.Additionally, the housing 206 is preferably separated into twocompartments 300, 302 by a partition 304. The partition 304 inconjunction with an air flow system to be described in greater detailbelow significantly inhibits migration of thermal energy from the secondcompartment 302 to the first compartment 300. Preferably, heat sensitivecomponents are placed in the first compartment 300 and heat generatingcomponents are mounted in the second compartment 302 so as to thermallyisolate the heat sensitive components from the heat generatingcomponents for optimal system performance.

FIG. 4 provides a detailed view of the chassis 202, as seen without thecomponents. As shown in FIG. 4, the chassis 202 contains a number ofpre-formed structures configured to receive and support the differentcomponents in the housing. Three circular recess 400 a–c are formed in afirst base portion 402 of the chassis 202 for mating with a PSA unit.Three corresponding divots 404 a–c are also formed in the first baseportion 402 immediately adjacent each respective recess 400 a–c. Thedivots 404 a–c extend laterally into each respective recess 400 a–c todirect gas flow in and out of the PSA unit in a manner to be describedin greater detail below. As such, the chassis serves as a manifold ofsorts for routing gases to and from the PSA unit. An annular compressormount 406 extends upwardly from a second base portion 408 of the chassis202 to provide an elevated mounting surface for a compressor assemblyand define an opening 410 sufficiently large to receive a portion of theassembly. As will be described in greater detail, the compressor mount406 is configured to support the compressor assembly in a manner suchthat transfer of vibrational energy from the compressor assembly to thehousing is reduced. As also shown in FIG. 4, an oblong slot 412 and abail 414 are formed adjacent the compressor mount 406 for receiving andsecuring a battery. In one embodiment, electrical mating contacts areformed in the slot 412 for connecting the battery to operatingcircuitry. In one embodiment, a battery circuit is mounted on the bottomof the slot which can also contain a IRDA transmitter/receiver.Moreover, the chassis 202 can also be fit with notches to receive andsupport the bottom of the partition.

Preferably, at least some of the above-described structures of thechassis 202 are integrally formed via an injection molding process so asto ensure dimensional accuracy and reduce assembly time. Thesepre-formed structures in the chassis advantageously facilitate assemblyof the components and help stabilize the components once they areassembled in the housing. In one embodiment, the chassis serves thefunction of providing an intermediary vibration isolation to thecompressor and motor. As shown in FIG. 4, the chassis has bottom mountsor vibration isolation feet 407 that are configured to engage with thebottom of the shell. Preferably, screws are inserted through the bottomof the shell and into the bottom of the vibration feet 407. In anotherembodiment, the chassis further comprises an integrated muffler forexhaust gas. Preferably, a recess is formed below the battery slot inwhich felt or other porous material is placed. As will be described ingreater detail below, an exhaust tube from the PSA unit is preferablyported directly into this recess and the felt serves to break up noisecoming from the release of pressurized waste gas.

FIG. 5 provides a detailed view of the components in the firstcompartment 300 of the housing 206. As shown in FIG. 5, the firstcompartment 300 generally contains an air intake 502, an intake filter504, and a PSA unit 506. The air intake 502 is an elongated tube coupledto the intake filter 504 and extending downwardly therefrom to receiveintake air. The intake filter 504 comprises a cylindrical shaped filterthat is preferably capable of removing particles greater than about 0.1microns from the intake air with about 93% efficiency. Moreover, theshape, density, and material of the intake filter 504 can be selected toprovide the filter with acoustic properties so that the filter can alsoserve as an intake muffler. As will be described in greater detailbelow, the intake filter 504 is in fluid communication with a compressorsystem and supplies the compressor system with filtered intake air. Boththe air intake 502 and the intake filter 504 are preferably mounted inthe first compartment 300 of the housing 206 so as to avoid drawinghigher temperature air produced by components in the second compartmentinto the system.

As FIG. 5 further shows, the PSA unit 506 generally includes a pair ofadsorbent bed columns 508 a, 508 b, a product gas storage column 510,and an integrated manifold 512 for controlling fluid flow to and fromthe columns 508 a–b, 510. Each adsorbent bed column 508 a–b comprises anelongated housing containing a nitrogen-selective adsorbent materialsuch as zeolite. The adsorbent bed columns 508 a–b are adapted to removenitrogen from intake air in a known manner in accordance with a PSAcycle so as to produce an oxygen rich product gas. The product gasstorage column 510 comprises an elongated housing adapted to receive andstore the oxygen rich product gas. In one embodiment, the product gasstorage column 510 also contains an adsorbent material capable ofholding a higher molar density of the product gas than an equivalent gasfilled chamber at equal pressure. As shown in FIG. 5, all three columns508 a–b, 510 are mounted side by side in the housing 206. Preferably,the columns 508 a–b, 510 have substantially the same length so that theintegrated manifold 512 can be mounted horizontally on the upper end ofthe columns 508 a–b, 510.

As will be described in greater detail below, the integrated manifold512 contains a plurality of integrated flow passages formed in a singleplane that permit fluid to flow to and from the columns 508 a–b, 510.The integrated manifold 512 also has a plurality of solenoid valves 514positioned in a single plane that control the flow of the fluid to andfrom the columns 508 a–b, 510 during a PSA cycle. As shown in FIG. 5,the integrated manifold 512 is mounted on the upper end of the columns508 a–b, 510 in a manner such that the integrated flow passages in themanifold are in fluid communication with openings in the upper end ofeach column. While the manifold 512 is positioned on only the upper endof the columns, gas flow from the manifold can enter the column housingthrough either the upper or lower end due to a novel single-ended columndesign to be described in greater detail below. In one embodiment, thevalves 514 of the manifold 512 contain a plurality of contact pins 516adapted for direct contact with a circuit board in a manner to be shownin greater detail below. A circuit board controlling the valves can bemounted directly on top of the manifold 512 without additional wires,which advantageously simplifies the assembly process and also allows forthe construction of a more compact device.

In one embodiment, an oxygen sensor 518 is mounted on the integratedmanifold 512 and ported directly into a product gas flow passage in themanifold 512. The oxygen sensor 518 is configured to measure the oxygenconcentration in the product gas using a galvanic cell or other knowndevices. Mounting the oxygen sensor 518 directly on the integratedmanifold 512 results in a more compact assembly as it eliminates the useof tubing and connectors that are typically required to interconnect theoxygen sensor to the PSA unit. Moreover, it also places the oxygensensor 518 closer to the product gas stream, which is likely to improvethe accuracy and response time of the sensor. In another embodiment, abreath detector 520 is also ported into the integrated manifold 512. Thebreath detector 520 generally comprises one pressure transducer thatsenses pressure change in the product gas downstream of the productdelivery valve (shown schematically in FIG. 1) caused by inhalation andexhalation of the patient so that the gas delivery frequency can beadjusted accordingly. The breath detector 520 may also include a secondpressure transducer that senses the storage vessel pressure which isused to drive the delivery of the product to the patient through theproduct delivery valve. The breath detector 520 ports directly into themanifold instead of tapping into the product line downstream, whichobviates the need of additional tubing connections and reduces the riskof leakage.

Advantageously, the PSA unit 506 has many novel features which,individually and in combination, contribute to a lighter, more compactand reliable apparatus. As shown in FIG. 5, the PSA unit 506 is mountedin the first compartment 300 which is thermally isolated from other heatgenerating components in the housing 206. Thermal isolation of the PSAunit 506 substantially prevents heat degradation of the valves 514 andother components in the unit. The PSA unit 506 is also configured withintegrated gas flow passages so as to substantially eliminate the use offlexible tubing, which in turn reduces the number of potential leakpoints. Moreover, the PSA unit 506 is designed to operate with a single,generally planar integrated manifold mounted horizontally on one end ofthe columns. The single manifold design reduces the amount of space thePSA unit occupies inside the housing and also reduces potential leakpoints. Additionally, the PSA unit 506 is configured to directly connectto a circuit board without additional wires, which further conservesspace and simplifies assembly.

FIG. 6 provides a detailed view of the adsorbent bed columns 508 a, 508b of the PSA unit, illustrating the novel single-ended column designbriefly described above. As shown in FIG. 6, the column 508 a generallyincludes an elongated adsorbent housing 602 having an upper end 604 anda lower end 606, each defining an opening through which gas can flow inand out of the housing 602. The column 508 a further includes anintegrated feed tube 608 extending from the upper end 604 of the housing602 to the lower end 606. The feed tube 608 provides a gas passagewaybetween the manifold and the housing 602 such that gas from the manifoldcan be routed through the feed tube 608 into the lower end 606 of thehousing 602 and vice versa. This design eliminates the need of a secondmanifold for directing gas into the lower end 606 of the housing 602 andallows all flow passages in the manifold to be co-located in a singleplane, which significantly reduces the number of tubing connections andpotential leak points in the unit.

The feed tube 608 preferably has a relatively small internal diameter tosubstantially minimize head space. It is generally recognized that thefeed passage in a PSA unit represents head space, which is undesirableas it penalizes system performance. In one embodiment, the feed tube 608has an internal diameter of about 0.125 inch and the adsorbent housing602 has a diameter of about 1.5 inch. Moreover, the adsorbent housing602 and the feed tube 608 are preferably integrally formed in anextrusion process so as to eliminate the use of flexible tubing andreduce potential leakage. In certain embodiments, the adsorbent bedcolumn 508 a further includes a plurality of threaded mounting members610 positioned adjacent the adsorbent housing 602 for mating with screwsthat attach the column 508 a to the chassis and manifold. The threadedmounting members 610 are preferably co-extruded with the housing 602 andthe feed tube 608 so as to simplify part construction.

As also shown in FIG. 6, the adsorbent bed housing 602 contains anadsorbent material 612, an upper and a lower restraining disk 614 a, 614b for inhibiting movement of the adsorbent material 612, a spring 616that applies pressure across the upper restraining disk 614 a to keepthe disk 614 a in position. In one embodiment, the adsorbent material612 comprises a granular material such as zeolite that can be easilydislodged. The restraining disks 614 a–b are preferably comprised of afrit material that can also serve as a filter for gross particulate,such as dislodged zeolite. Each restraining disk 614 a–b has a diameterselected to form an interference fit with the internal walls of thehousing 602 and has a thickness of at least about 0.2 inch, to providesome resistance to tilting of the disk, which may lead to leaks ofparticulate. The thickness of the disk 614 a–b coupled with the natureof the frit material provide a tortuous path for particulate to travelthrough, which increases the effectiveness in trapping the particulateas compared to conventional paper filters. As also shown in FIG. 6, theupper restraining disk 614 a is pressed against the adsorbent material612 by the spring 616. The spring 616 is preferably a wave springconfigured to apply substantially uniform pressure across the surface ofthe upper restraining disk 614 a, so as to substantially inhibit thedisk from tilting.

As also shown in FIG. 6, the adsorbent bed column 508 a further includesannular gaskets 616 a, 616 b positioned adjacent to and in sealingengagement with the ends 604, 606 of the column 508 a to contain thepressurized gases therein. In one embodiment, each annular gasket 616a–b further comprises an integrally formed filter portion 618 a, 618 bfor filtering smaller particulate that cannot be captured by therestraining disks 614 a–b. Preferably, the filter portion is capable offiltering particles greater than about 70–120 microns. In oneembodiment, the gasket 616 a–b is made of a silicone material and thefilter portion 618 a–b comprises a woven fabric, woven screen, or thelike that is cast or molded together with the gasket. In anotherembodiment, the gasket 616 a–b and filter portion 618 a–b for all threecolumns of the PSA unit are injection molded as a single piece as shownin FIG. 6. Preferably, the filter portion 618 a–b is embedded in thegasket 616 a–b so as to facilitate placement of the filter portion andensure a reliable seal between the gasket and the filter portion.Moreover, openings 620 are formed in each gasket 616 a–b to accommodateopenings in the feed tubes and the threaded mounting members.

FIGS. 7A and 7B provide schematic illustrations of the adsorbent bedcolumn 508 a in combination with the chassis 202 and the manifold 512,showing the manners in which gas flow is directed in and out of thecolumn 508 a in accordance with the single-ended column design. As shownin FIG. 7A, feed gas 702 is directed from a feed stream 704 in themanifold 512 into an upper opening 706 of the feed tube 608. The feedgas 702 travels downwardly through the tube 608 and is diverted by adivot 404 a in the chassis 202 into a recess 400 a underneath the lowerend 606 of the adsorbent housing 602. The divot 404 a, which ispre-formed in the chassis 202, advantageously serves as a lateral gasflow passageway so as to eliminate the need of any flexible tubing onthe lower end of the column, which in turn simplifies assembly andreduces potential leak points. The feed gas 702 flows upwardly from therecess 400 a through the lower end 606 of the housing 602 and upwardlythrough the adsorbent material contained in the housing 602. Theadsorbent material selectively removes one or more components in thefeed gas 702 in a known manner to form a product gas 708. The productgas 708 flows out of an upper end 604 of the housing 602 into a productstream 710 in the manifold 512. FIG. 7B shows the manner in which purgegas is directed in and out of the column. As shown in FIG. 7B, purge gas712 from a product stream 714 in the manifold 512 is directed throughthe upper end 604 of the housing 602 downwardly into the housing 602 toflush out the gas therein. The purge gas 712 exits the lower end 606 ofthe housing 602 and is channeled through the divot 404 a. The divot 404a directs the purge gas 712 to flow into a lower opening 716 of the feedtube 608. The purge gas 712 exits the feed tube 608 through its upperopening 706 and enters a waste stream 718 in the manifold 512. As FIGS.7A and 7B illustrate, the single-ended column design in conjunction withthe divot formed in the chassis allow gas from a single-planed manifoldto enter and exit the adsorbent housing through either the upper orlower end of the housing.

FIG. 8 provides a detailed view of the integrated manifold 512 of thePSA unit. As shown in FIG. 8, the integrated manifold 512 generallyincludes an upper plate 802 and a lower plate 804, each having groovesformed in an inner surface thereof. The grooves of the lower plate alignwith those of the upper plate so as to form fluid passages in themanifold 512 when the upper plate 802 is affixed to the lower plate 804.The fluid passages may include feed gas pathways, waste gas pathways,and gas pathways interconnecting the adsorbent columns. The specificpattern of the fluid passages in the manifold can vary, depending on theparticular application, although the passages of the preferredembodiment correspond to the circuit of FIG. 1. As also shown in FIG. 8,the upper plate 802 has a feed gas inlet 812 through which pressurizedair from the compressor system is directed into the manifold 512. Thelower plate 804 has a waste gas outlet 814 through which exhaust gas isexpelled from the manifold 512 and a plurality of openings to connectthe fluid passages with the adsorbent columns. Solenoid valves 816 aremounted on an upper surface 818 of the upper plate 802 in a known mannerto control the flow of fluid between the fluid passages and the PSAcolumns. Bores 820 are also formed in the upper and lower plates 802,804 for receiving fasteners used to mount the plates together and ontothe PSA columns. In one embodiment, the plates 802, 804 of the manifold512 are made of a plastic material formed by injection molding andlaminated together via an adhesive bond applied in a vacuum. Whencompared to conventional laminated manifolds that are typicallyconstructed of machined metal plates, the integrated manifold 512 formedby injection molding is advantageously lighter and less costly tomanufacture.

FIG. 9 schematically illustrates a water trap system 900 integrated inthe manifold 512 for removing moisture from the feed gas prior todelivery to the columns. As shown in FIG. 9, the water trap system 900generally includes an integrated water trap 902 formed in the manifold512 and in fluid communication with a feed gas pathway 904. The watertrap 902 is adapted to trap condensed water 906 in the feed gas bygravity so as to prevent the water from reaching the adsorbent bed 908.Preferably, the water trap 902 is located in a waste gas pathway 910such that expelled waste gas carries the condensed water out through theexhaust.

In one embodiment, the water trap 902 is configured as a recess in thelower plate 804 of the manifold 512, extending downwardly from a sectionof the feed gas pathway 904 located in the upper plate 802. The watertrap 902 is positioned at a lower elevation relative to the feed gaspathway 904 so as to substantially prevent trapped water 906 fromre-entering the feed gas pathway 904. In certain embodiments, a baffle912 is positioned in the feed gas pathway 904 to divert the feed gasflow downwardly into the water trap 902 so that the gas is required torise upwardly to return to the feed gas pathway 904, which substantiallyprevents any condensed water from being carried past the water trap bythe feed gas flow. As also shown in FIG. 9, the water trap 902 is inline with the waste gas pathway 910 located in the lower plate 804 ofthe manifold 512 so that the water trap 902 can be purged by waste gasflowing through the pathway 910. In one embodiment, the water trap 902is located in center of a three way junction formed by the airflowpassages to and from the feed valve, the exhaust valve, and theconnection to the top of the column.

In operation, feed gas 914 enters the manifold 512 through the feed gasinlet 812 in the upper plate 802 and is directed through a solenoidvalve 816 into the feed gas pathway 904. The feed gas 914 flows acrossthe recessed water trap 902 such that condensed water 906 in the feedgas 914 settles into the water trap 902 by gravity while the lightercomponents continue along the pathway 904 into the adsorbent bed 908.Preferably, the water trap 902 containing the condensed water 906 issubsequently purged by gas in the waste gas pathway 910. It will beappreciated that the integrated water trap system is not limited to theabove-described embodiment. Any integrated water trap system thatencompasses the general concept of forming an integrated gas flow pathhaving a lower region where light air flows past and moisture aircondenses due to gravity are contemplated to be within the scope of theinvention.

FIG. 10 schematically illustrates a piloted valve system 1000 integratedin the manifold 512 for providing quick release of pressurized gas fromthe adsorbent columns during a PSA cycle. It is generally recognizedthat the efficiency of a PSA cycle benefits from fast release of thepressurized gas within the adsorbent columns during the blow down andpurge steps. However, the solenoid valves controlling gas flow from thecolumns to the waste gas pathway are typically limited in orifice sizewhich in turn results in restricted flow and slowed release of the gaswithin the columns. To increase the flow capacity, the piloted valvesystem 1000 shown in FIG. 10 utilizes a solenoid valve to drive a muchlarger piloted valve that is embedded in the manifold and controls thewaste gas flow to and from the columns.

As shown in FIG. 10, the piloted valve system 1000 generally includes asolenoid valve 1002, an air chamber 1004 in fluid communication with thesolenoid valve 1002, and a piloted valve 1006 that can be actuated bythe solenoid valve 1002 through the air chamber 1004. The piloted valve1006 preferably comprises a diaphragm 1006 positioned between the airchamber 1004 and a waste gas pathway 1008. Pressure differences betweenthe air chamber 1004 and the waste gas pathway 1008 mechanically deflectthe diaphragm 1006 to open or close the waste gas pathway 1008 to gasflow. Preferably, the diaphragm 1006 has a natural resiliency such thatit is deflected away from the waste gas pathway 1008 when the airchamber 1004 is not pressurized.

In one embodiment, the diaphragm 1006 is seated in a recess 1010 thatextends downwardly from an exterior surface 1012 of the upper plate 802.An insert 1014 is mounted in the recess 1010 above the diaphragm 1006and flush with the exterior surface 1012 of the plate 802. The diaphragm1006 has an outer rim 1016 that sealingly engages with an inner surface1018 of the insert 1014 so as to form the air chamber 1004 as shown inFIG. 10. The insert 1014 contains a plurality of openings 1020 that arein fluid communication with the air chamber 1004. The solenoid valve1002 is mounted above the insert 1014 and controls gas flow through theopenings 1020 to the air chamber 1004.

As also shown in FIG. 10, the waste gas pathway 1008 is formed in thelower plate 804 of the manifold and in contact with the diaphragm 1006through an opening 1022 formed in the inner face 808 of the upper plate802. To close the waste gas pathway 1008 from gas flow, the diaphragm1006 is deflected toward a baffle 1024 positioned in the waste gaspathway 1008 and sealingly engages with the baffle 1024 so as to blockoff a pathway 1026 between the diaphragm and the baffle. To open thewaste gas pathway 1008, the diaphragm 1006 is deflected away from thebaffle 1024 so as to allow gas to flow through the pathway 1026 and outthe exhaust. It will be appreciated that the pathway 1026 controlled bythe diaphragm 1006 provides a much large flow capacity for waste gasthan the orifices in the solenoid valves.

In operation, pressurized purge gas 1028 from the adsorbent column flowsinto the opening 1022 in the upper plate 802 and pushes the diaphragm1006 away from the baffle 1024 so as to open the path 1026 between thediaphragm 1006 and the baffle 1024 for gas flow. After the purge gas isreleased through the exhaust, a portion of the feed gas is directed intothe air chamber 1004 via the solenoid valve 1002 to push the diaphragmagainst the baffle 1024 so as to close the path 1026 therebetween.Advantageously, the piloted valve system 100 allows waste gas to bereleased from the column through a much larger opening than the orificescontained in the solenoid valves and does not consume additional spaceas the valves are all incorporated in the manifold.

FIG. 11 provides a detailed view of the components inside the secondcompartment 302 of the housing 206. As shown in FIG. 11, the secondcompartment 302 generally contains an air circulation fan 1102, abattery 1104, and a compressor assembly 1106. In one embodiment, the fan1102 comprises a blower or other device used for forcing aircirculation. The battery 1104 is preferably a lithium ion battery havinga rated life of at least 2 hours. In certain embodiments, the batterymay also comprise a fuel cell or other transportable electric powerstorage device. The compressor assembly 1106 includes a compressor 1108,a driving motor 1110, and a heat exchanger 1112. In one embodiment, thecompressor 1108 is preferably a non-reciprocating compressor such as ascroll compressor or a radial compressor and the motor 1110 ispreferably a DC brushless motor. In certain embodiments, the compressor1108 can also be a vacuum pump or a combination of a vacuum pump and acompressor. The heat exchanger 1112 can be in the form of aluminumcoiled tubes or other common heat exchanger designs. In one embodiment,the heat exchanger 1112 has an inlet 1114 and an outlet 1116. The inlet1114 is in fluid communication with the compressor 1108 for receivingfeed gas therefrom and the outlet 1116 is connected to the PSA unit fordelivery feed gas thereto.

As also shown in FIG. 11, the compressor 1108 rests on an upper surface1118 of the compressor mount 406, which is elevated above the base 208of the housing. The driving motor 1110 attached to the compressor 1108extends into the opening 410 in the compressor mount 406 and remainssuspended therein. Moreover, the heat exchanger 1112 is positioned abovethe compressor 1108 and under the fan 1102. Preferably, the fan 1102directs an air flow against the heat exchanger 1112 to facilitatecooling of the feed gas therein. As also shown in FIG. 11, the battery1104 is mounted on the battery bail 414 via three pairs of guide rails1120 formed on the battery and adapted to mate with the battery bail414. The distance between the guide rails 1120 becomes progressivelyshorter from bottom to top, with the topmost pair forming the tightestfit with the bail 414. This facilitates mounting of the batteryparticularly for those with impaired dexterity. When the battery 1104 isin position, the topmost guide rails are held firmly by the bail 414while a lower section 1130 of the battery 1104 is held firmly by themated electrical connectors formed in the battery slot 412.

In one embodiment, a compressor restraint 1122 is connected between thecompressor 1108 and the chassis 202 to secure the compressor 1108 to thehousing 206. Preferably, the compressor restraint 1122 comprises anelastic tether that fastens the compressor 1108 to the chassis.Preferably, the chassis is fit with grooves for engaging with thecompressor restraint. In one embodiment, the compressor restraint 1122comprises two elongated legs 1124 a, 1124 b spaced apart in the middleand joined together in an upper end 1126 a and a lower end 1126 b. Theupper end 1126 a is removably attached to the compressor 1108 and thelower end 1126 b removably attached to the chassis 202. Moreover, theelongated legs 1124 a, 1124 b preferably have preformed bends whichextend away from each other. These bends can be pressed toward eachother to straighten the legs and increase the overall length of thecompressor restraint 1122 so as to facilitate mounting and removal ofthe compressor restraint. Preferably, the compressor restraint does notsubstantially exert active force on the compressor assembly when thehousing is in its upright position so as to reduce vibration couplingfrom the compressor to the chassis.

In another embodiment, a vibration damping member 1128 is interposedbetween the compressor mount 406 and the compressor 1108 to furtherreduce transfer of vibrational energy from the compressor to thehousing. As shown in FIG. 12, the vibration damping member 1128comprises a grommet 1202 configured to mate with the annular compressormount so as to provide a vibration damping mounting surface for thecompressor system. Preferably, the grommet 1202 is made of a resilientsilicone material such as sorbothane and configured to absorb lowvibrational frequencies produced by the compressor. In one embodiment, afirst set of ribs 1204 are formed along the periphery of an uppersurface 1206 of the grommet 1202 and configured to absorb vibration fromthe compressor. In another embodiment, a second plurality of ribs 1208are formed on an inner surface 1210 of the grommet 1202 and configuredto absorb vibration from the motor. The ribs 1204, 1208 substantiallyreduce the amount of vibration transferred to the grommet 1202 which isin contact with the compressor mount. The compressor advantageouslyrests on the grommet without being pressed against the chassis duringnormal operations and is restrained by the compressor restraint onlywhen the apparatus is tipped over on its side. The vibration dampingmember 1128 is advantageously configured to reduce transfer of vibrationenergy, particularly low frequency vibration, from the compressor systemto the housing, thus reducing noise created by vibration of the housing.

In addition to vibration control features, the apparatus alsoincorporates one or more thermal management systems to provide coolingfor temperature sensitive components inside the housing and facilitateheat dissipation. FIG. 13 illustrates a thermal management system of onepreferred embodiment adapted to provide cooling for the battery. Athermal sleeve 1302 is positioned around the battery 1104 to isolate airsurrounding the battery 1104 from higher temperature air in the secondcompartment 302 of the housing. A lower end 1304 of the thermal sleeve1302 is configured to mate with the battery slot 412 so as to close offthe lower opening of the sleeve and form a compartment or air pocket forthe battery. A cooling gas is preferably directed into the space betweenthe thermal sleeve 1302 and the battery 1104 to facilitate dissipationof heat generated by the battery and also to insulate the battery fromheat generated by other components in the housing.

In one embodiment, a conduit 1306 extends from the exhaust outlet 814 ofthe PSA unit 506 to an opening 1038 in the battery slot 412. The conduit1306 directs exhaust gas 1312 from the PSA unit 506 into the spacebetween the thermal sleeve 1302 and the battery 1104. Since the exhaustgas is typically cooler than ambient air surrounding the batterycompartment, it serves as an efficient source of cooling air for thebattery. The exhaust gas enters the thermal sleeve 1302 from the loweropening 1308 in the battery slot 412 and circulates out of the upper end1310 of the thermal sleeve 1302.

As also shown in FIG. 13, a circuit board 1314 is mounted horizontallyon the PSA unit 506, above the valves 816 on the manifold 512. Thecircuit board 1314 comprises control circuitry which governs theoperation of the PSA unit, alarms, power management system, and otherfeatures of the apparatus. As described above, contacts on the circuitboard 1314 are in direct electrical contact with mating contacts 516 onthe valves 514 of the PSA unit 506, which conserves space and eliminatesthe need for wiring connections. In one embodiment, the circuit board1314 has small through-hole connectors that align with the location ofvalve pins to establish electrical interconnection.

As will be described in greater detail below, the circuit board 1314 islocated in the path of a directed air flow inside the housing so as tofacilitate heat dissipation of the circuits during operation. Moreover,although the control circuitry is substantially entirely within thefirst compartment 300, the circuit board 1314 extends horizontally fromthe first compartment 300 to the second compartment 302, substantiallycovering the upper openings of both compartments so as to inhibitmigration of higher temperature air from the second compartment 302 intothe first 300. In one embodiment, foam material is placed between theouter edges 1316 of the circuit board 1314 and the inner walls of thehousing to form an air seal which further inhibits migration of airbetween the compartments 300, 302. In another embodiment, the circuitboard 1314 is shaped to mirror the cross-sectional contour of thehousing so as to ensure an effective seal between the circuit board 1314and housing.

FIG. 14 schematically illustrates a thermal management system of anotherpreferred embodiment, which is configured to provide a continuous flowof cooling air across the components inside the housing. As shown inFIG. 14, ambient air 1402 is drawn into the housing 206 through an airinlet 1404 by the fan 1102. The air inlet 1404 is preferably located ina lower portion of the sidewall 212 c adjacent the first compartment300. The ambient air 1402 is directed to flow through an air flowpassageway 1406 generally defined by the walls of the housing and thecomponents therein. The air flow passageway 1406 is preferably acircuitous path extending from the air inlet 1404, through the first andsecond compartments 300, 302, to an air outlet 1408 located in a lowerportion of the sidewall 212 a adjacent the second compartment 302.Preferably, the ambient air is directed to flow across the firstcompartment, which contains temperature sensitive components, beforeentering the second compartment which contains heat generatingcomponents. As will be described in greater detail below, the thermalmanagement system utilizes the air circulation fan 1102 in combinationwith the configuration of the housing and placement of componentstherein to produce a one-way flow passageway for air from inlet tooutlet. As such, heated air, is not re-circulated back into the systemand the components are cooled by a continuous stream of external air.

In one embodiment, the air flow passageway 1406 has an upstream portion1408 and a downstream portion 1410. The upstream portion 1408 includes avertical path 1406 a generally defined by the PSA unit 506 and thesidewall 212 c of the housing 206 followed by a horizontal path 1406 bgenerally defined by the circuit board 1314 and the upper wall 210. Thedownstream portion 1410 includes a vertical path 1410 a generallydefined by the partition 304 and the battery 1104, a horizontal path1410 b generally defined by the compressor assembly 1106 and the base208 of the housing, and followed by another vertical path 1410 c definedby the battery 1104 and the sidewall 212 a. Air in the upstream portion1408 of the passageway 1406 preferably has a lower temperature than airin the downstream portion 1420 where most heat generating components arelocated. Temperature sensitive components such as the valves 514 andelectrical components disposed on the circuit board 1314 areadvantageously disposed in the upstream portion 1408, thereby exposingthe valves and components to a continuous stream of incoming coolingair, which reduces their thermal load. Preferably, the upstream portion1408 of the air flow passageway 1406 is thermally isolated from thedownstream portion 1410 by the partition 304 and the circuit board 1314in conjunction with a directed air flow described below.

As also shown in FIG. 14, the fan 1102 is located in the downstreamportion 1410 of the air flow passageway 1406 immediately above thecompressor assembly 1106. The fan 1102 generates a downward air streamdirectly against the compressor assembly 1106 to facilitate heatdissipation of the heat exchanger and compressor. The air stream flowspast the compressor assembly 1106 through the downstream portion 1410 ofthe air passageway 1406 and exits the housing 206 through the air outlet1408. The fan 1102 is advantageously positioned to focus a cooling airstream directly on the heat generating components inside the housing.Moreover, portions of the air stream warmed by the compressor assemblyare not re-circulated inside the housing, which substantially minimizesincreases in the ambient temperature therein and improves coolingefficiency. The air stream generated by the fan 1102 creates a negativepressure in the upstream portion of the passageway 1406, which drawsambient air through the passageway 1406 from the first compartment 300to the second compartment 302 as shown in FIG. 14. Although someturbulence of the air may occur downstream of the fan, the air pathconfiguration permits substantially one way air flow along the pathbetween the intake and the fan.

In certain embodiments, noise reduction features are also implemented inthe apparatus. As shown in FIG. 14, a series of sound absorbing baffles1412 are positioned along the air flow pathway 1406 to reduce noisecaused by the air flow inside the housing. Moreover, the air flowpassageway is configured with a circuitous path so as to further abatethe noise generated by the air flow. The circuitous path advantageouslyprovides for air movement through the housing, but makes it difficultfor sound to propagate or reflect off internal surfaces of the housingand make its way out of the housing.

FIG. 15 schematically illustrates the manner in which intake air 1500 isprocessed through the components of the apparatus. As shown in FIG. 15,intake air 1500 is drawn through the air intake 502, through the airfilter 504 into an inlet port 1404 of the compressor 1108. Air ispreferably drawn into the compressor air intake at a flow rate of nogreater than about 15 slpm so as to maintain a low noise level and lowpower consumption throughout the system. The air is pressurized by thecompressor 1108 and delivered to the heat exchanger 1112 through thecompressor outlet 1406. The pressurized air is cooled by the heatexchanger 1112 and then supplied as feed gas to the PSA unit 506. Feedgas is directed through the inlet port 812 of the PSA unit 506, intoadsorbent columns 508 a–b to produce a product gas in accordance with aPSA cycle, preferably the six step/two bed cycle described above.Product gas from the adsorbent columns 508 a–b flows into the storagecolumn and is delivered to the patient through an outlet port 1408 inthe manifold 512 connected to the storage column. Preferably, theproduct gas is delivered to the patient at a flow rate of between about150 ml/minute and 750 ml/minute and having an oxygen concentration of atleast 87%, more preferably between 87%–93%.

FIG. 16A shows the apparatus as fully assembled in the form of aportable oxygen concentrator unit 1600. The unit 1600, including thehousing and components therein, has a combined weight of preferably nomore than about 10 pounds and produces a noise level of no greater thanabout 45 dB external to the unit. As shown in FIG. 16A, an air scoop1602 is integrally formed in the sidewall 212 c of the shell 204adjacent the air outlet 1408 to channel air flow out of the housing 206.A similar air scoop is also formed in the sidewall adjacent the airinlet (not shown) to channel ambient air into the housing. As describedabove, the sidewalls 212 a, c of the housing have a curved configurationso as to discourage users from resting the housing against the sidewall,which can block the air inlet or outlet.

As also shown in FIG. 16A, a user interface panel 1603 containing aplurality of system controls 1604 such as flow rate and on-off switchesis integrally formed in the shell 204. In some embodiments, an I/O port1606 is preferably formed in the user interface panel 1603. The I/O portallows data transfer from the unit to be performed simply by using acomplementary device such as a palm desktop assistant (PDA) or laptopcomputer. Moreover, an in-line filter system 1608 is also formed in theshell 204 to filter product flow in line prior to delivery to thepatient. As will be described in detail below, the in-line filter system1608 is integrated in the shell 206 of the unit so as to provide easyaccess to the filter without requiring opening of the shell.

As shown in FIG. 16B, the in-line filter system 1608 includes an annularchamber 1610 formed in the shell 204 and a fitting 1612 that engageswith the chamber 1610 from outside of the shell. The chamber 1610 has aseat portion 1613 configured to receive a disk filter 1614 and athreaded portion 1616 configured to engage with the fitting 1612.Preferably, the chamber 1610 is molded into the shell 204 and oxygenproduct inside the housing is ported to the chamber. In one embodiment,the disk filter 1614, preferably a 10 micron or finer filter, is held incompression in the seat portion 1613 of the chamber by the fitting 1612,which threadably engages with the chamber 1610 from outside of theshell. In another embodiment, the fitting 1612 also contains a hose barb1618 used to connect the cannula. Advantageously, the disk filter 1614can be serviced by simply unscrewing the fitting 1612, replacing thefilter 1614, and then re-screwing the fitting 1612 without ever havingto open the housing of the unit. As shown in FIG. 16C, the unit 1600also includes a removable hatch 1620 that provides simplified access tothe circuit board 1314 inside the housing 206 and the internalconnections to the oxygen product line and power input.

FIG. 17 schematically illustrates a satellite conserver system 1700 thatcan be used in conjunction with the oxygen concentrator unit 1600 todeliver oxygen to users. It is generally recognized that oxygenconcentrators deliver a finite rate of oxygen product which must bemetered to the user through a conserving device. A conserving device istypically mounted inside the concentrator and includes a breath sensorthat senses breath inhalation of the user to determine the timing andquantity of each bolus delivery. The sensitivity of the breath sensor issignificant to the efficacy of the conserving device. As such, mostconserving devices require that users use no longer than a 10 feet tubeconnected to the nasal cannula to ensure that the conserving deviceinside the concentrator can accurately sense the breath of the user.

The satellite conserver 1700 is configured to substantially remove theconstraint imposed by the short tube requirement and allow users thefreedom to move in a much larger area around the portable concentrator.As shown in FIG. 17, the satellite conserver 1700 includes a small,lightweight conserving device 1702 for delivering oxygen rich productgas to users in metered amounts in a known manner in response to sensedbreath. The conserver 1700 includes a breather sensor 1701 for sensingthe user's breath and a delivery valve 1703 for delivering oxygen to theuser. In one embodiment, the conserving device 1702 utilizes a breathrate algorithm that delivers a nearly constant amount of oxygen perminute, regardless of the breath rate of the patient. As such, patientswho take more breaths within a given time period receive the same amountof oxygen as those who take less breaths. In another embodiment, theconserving device adjusts the bolus volume based on the flow settingrather than the breathing rate. In yet another embodiment, theconserving device 1702 can be fit with a second pressure sensor, whichdetects the pressure in the input line from the concentrator. Thedelivery valve timing can be adjusted based on the sensed pressure atthe end of the input line such that a higher pressure corresponds to ashorter valve open time and a lower pressure corresponds to a longervalve open time.

As also shown in FIG. 17, the conserving device 1702 is adapted to beworn by the user or positioned adjacent to the user so that breathsensing functions can be performed proximate to the user even if theconcentrator unit is far away. Thus, the sensitivity of the breathsensor is not compromised even if the user is far way from the unit. Thesatellite conserver 1700 further includes flexible tubing 1704connecting the conserving device 1702 to the hose barb fitting 1612 onthe concentrator 1600. In one embodiment, the tubing 1704 is preferablybetween 50 to 100 feet, which provides users a much greater radius ofmobility. When the satellite conserver 1700 is in use, the breathdetector mounted inside the housing of the concentrator is disabled. Asalso shown in FIG. 17, the satellite conserver can be worn on the personby a clip 1706 attached to the conserving device 1702. The satelliteconserver advantageously permits the user to move around the vicinity ofthe concentrator, preferably in at least a 50 to 100 feet radius,without detracting from the efficacy of the unit.

FIG. 18A schematically illustrates a mobility cart 1800 configured totransport an oxygen concentrator unit for users traveling away fromhome. As shown in FIG. 18A, the mobility cart 1800 includes a generallyrectangular frame 1802 attached to a plurality of wheels 1804 so as topermit rolling movement of the frame 1802 over the ground. As also shownin FIG. 18A, the frame 1802 has a support portion 1806 adapted forreceiving an oxygen concentrator unit and a handle portion 1808extending upwardly from the support portion 1806 for users to hold whenmoving the cart. The support portion 1806 preferably contains acompartment 1810 configured to seat the oxygen concentrator and at leasttwo slots 1812 configured to seat and secure spare batteries. In oneembodiment, a battery bail 1814 is placed in each slot 1812 for securingthe batteries in the manner described above. In another embodiment, asmall recess 1816 is formed in the back of the compartment 1810 forholding the satellite conserver, spare cannulas or filter.

As also shown in FIG. 18A, the mobility cart 1800 further includes anon-board power supply 1818 that is attached to the frame 1802 portion.Preferably, the power supply 1818 has an AC power input and is adaptedto power charging terminals fitted in each battery slot 1812 and aterminal fitted in the compartment for charging the battery within theconcentrator. In one embodiment, the cart also has an adapter plug 1820that extends from the power supply 1818 and mates with theconcentrator's DC power input jack. The power supply 1818 is preferablysufficient to power both battery chargers while simultaneously poweringthe concentrator unit and charging the battery mounted inside the unit.Each battery preferably has a rated life of at least 2 hours so that theuser is able to enjoy continuous use of the concentrator unit for atleast six hours without an external power source. In one embodiment, thepower supply is cooled by a fan mounted on the frame portion 1802. Inanother embodiment, the frame portion has recesses through which watermay drain out without damaging the parts. The cart 1800 can furthercomprise an integrated power cord and/or retractable power cord that isadapted to be plugged into a wall.

FIG. 18B illustrates the manner in which the oxygen concentrator 1600and spare batteries 1822 are positioned in the mobility cart. As alsoshown in FIG. 18B, the handle 1808 has two telescoping rails that can beextended and retracted. When the handle 1808 is in the fully retractedposition as shown in FIG. 18B, the mobility cart 1800 preferably has aheight of about 14–18 inches and can be stored in a small area such asunder an airplane seat. In one embodiment, the mobility cart isstructured such that the concentrator, when sitting in the cart,interfaces closely with seals positioned on the frame of the cart at theair intake and exhaust ports. As such, airflow coming into or out of theconcentrator actually travels through the frame in some manner, addingextra sound attenuation by increasing the tortuosity of the flow path.Moreover, an auxiliary fan or blower mounted in the cart can also beused to circulate this air further. Advantageously, the mobility carthas integrated battery chargers and power supply incorporated in oneunit so as to obviate the need for users to pack power supplies orexternal chargers when traveling with their concentrator. Moreover, thecart provides a single compact unit in which all oxygen concentratorrelated parts can be transported, which allows users greater ease ofmobility when traveling.

Although the foregoing description of certain preferred embodiments ofthe present invention has shown, described and pointed out thefundamental novel features of the invention, it will be understood thatvarious omissions, substitutions, and changes in the form of the detailof the system, apparatus, and methods as illustrated as well as the usesthereof, may be made by those skilled in the art, without departing fromthe spirit of the invention. Consequently, the scope of the presentinvention should not be limited to the foregoing discussions.

1. A portable gas fractionalization apparatus, comprising: a PSA unitcomprising plural adsorbent beds which produce oxygen having a purity ofat least 87%, said unit including valves operating in accordance with aPSA cycle that includes a pressure equalization step so as to providegreater than about 31% recovery of oxygen from air; a compressorconnected to supply compressed air to said PSA unit, said compressorbeing non-reciprocating to reduce compressor noise, wherein thecompressor is configured to draw ambient air at a flow rate of no morethan about 15 slpm; a blower which produces an air stream across saidcompressor, wherein said valves of said PSA unit are disposed upstreamof said air stream across said compressor such that thermal load on saidPSA valves is reduced.
 2. The apparatus of claim 1, wherein the pluraladsorbent beds of said PSA unit comprise two adsorbent beds, whereinsaid PSA cycle is a six-step PSA cycle.
 3. The apparatus of claim 2,wherein said PSA unit provides greater than about 31% recovery of oxygenfrom air comprises providing between about 31%–38% recovery of oxygenfrom air.
 4. The apparatus of claim 2, wherein said PSA unit comprisingplural adsorbent beds which produce oxygen having a purity of at least87% comprises producing oxygen having a purity of between about 87%–93%.5. The apparatus of claim 1, wherein said compressor comprises a scrollcompressor.
 6. The apparatus of claim 1, further comprising a heatexchanger which cools the compressed air to about the temperature ofsaid ambient air prior to supplying said compressed air to the PSA unit.7. The apparatus of claim 1, further comprising a product gas deliverysystem, which delivers said oxygen to a patient at a flow rate ofbetween about 0.15–0.75 slpm.
 8. The apparatus of claim 7, wherein theapparatus further comprises a microprocessor control for collecting andrecording data on apparatus performance or usage and an infrared I/Oport for transmitting said data to a remote location.
 9. A portable gasfractionalization apparatus, comprising: a housing having an air inletand an air outlet, said housing containing components including acompressor, plural adsorbent beds, a battery having a rated life of atleast 2 hours, said compressor is powered by the battery so as to drawair into said compressor at a rate of about 15 slpm or less, saidhousing and said components having a combined weight of less than about10 pounds; wherein said housing is configured such that noise producedexterior to the fractionalization apparatus is no more than about 45 dB.10. The apparatus of claim 9, further comprising a blower which isconfigured to draw ambient air through said air inlet to provide coolingfor the components.
 11. The apparatus of claim 10, wherein said housingcomprises a circuitous air flow passageway for the ambient air to flowthrough, said circuitous passageway extending between the air inlet andthe air outlet and configured to reduce noise due to air flow.
 12. Theapparatus of claim 9, wherein said compressor comprises a scrollcompressor.
 13. The apparatus of claim 12, wherein said compressor drawsair into said compressor at a rate of about 15 slpm or less and deliversa feed gas at a flow rate of between about 4 to 9 slpm and at a pressureof about 35 psia while generating a noise level of less than about 35 dBexternal to said compressor.
 14. The apparatus of claim 9, wherein saidhousing comprises a plurality of sound baffles.
 15. The apparatus ofclaim 9, wherein said housing comprises a vibration damper adapted toreduce transfer of vibrational energy from the compressor to thehousing.
 16. A method of producing an oxygen rich gas, comprising:providing ambient air to a non-reciprocating compressor, wherein saidambient air is drawn into the compressor at a flow rate of less thanabout 15 slpm, wherein said compressor pressurizes the ambient air anddelivers the pressurized air to a PSA unit at a flow rate of betweenabout 4 to 9 slpm; and processing said pressurized air in the PSA unitin accordance with a PSA cycle so as to produce an oxygen rich gashaving a purity of between about 87%–93%.
 17. The method of claim 16,wherein said PSA cycle includes a pressure equalization step.
 18. Themethod of claim 17, wherein said PSA cycle is a six-step/two-bed PSAcycle.
 19. The method of claim 16, wherein said PSA unit operating inaccordance with the PSA cycle provides greater than about 31% recoveryof oxygen from said ambient air.
 20. The method of claim 16, whereinsaid compressor generates a noise level of less than about 35 dBexternal to the compressor when pressurizing the ambient air.
 21. Themethod of claim 16, further comprising generating an air stream acrosssaid compressor to providing cooling for the compressor.